Hundreds of wildfires burning in Canada are undermining U.S. air quality across the Upper Midwest and Northeast, making skies hazy from Detroit to New York City and even prompting a ground stop at Boston's Logan International Airport due to "low visibility.

Air quality alerts are in effect in the Philadelphia area, fueled by smoke from wildfires that are burning thousands of miles away.

Wildfires burning in Canada were causing unhealthy air quality across parts of North America on Monday. By Judson Jones Judson Jones is a meteorologist and reporter for The Times. Canadian wildfires burning across northern Manitoba and Saskatchewan are sending smoke through central Canada,